PROJECT SUMMARY Dysarthria negatively impacts functional communication and social participation for over 50% of children with cerebral palsy (CP). Although dysarthria is a disorder of speech movement, very little is known about the biomechanical factors that underlie reduced intelligibility in children with dysarthria. This lack of knowledge is a fundamental barrier to developing more effective assessment and intervention strategies. The proposed research aims to address this need by identifying biomechanical constraints that limit precise articulation and intelligible speech in children with CP. In addition, the study aims to determine the efficacy of a kinematic index of articulatory distinctiveness for quantifying articulatory imprecision in children with CP. Specific Aim 1 will use four kinematic measures (i.e., range, speed, duration, and inter-articulator coupling) of lip, tongue, and jaw movement to identify articulatory constraints in connected speech of children with dysarthria secondary to CP relative to typically-developing children, and to identify kinematic measures that contribute most to reduced speech intelligibility. We hypothesize that children with dysarthria will use inefficient movement patterns (i.e., increased or equal movement range and speed, longer durations) and have reduced coordinative flexibility (i.e., increased coupling between articulators) in sentence production, compared to typically- developing children, and that measures of articulatory coordination will best predict intelligibility. Specific Aim 2 will use the variation in tongue coupling relations across a comprehensive set of consonant and vowel contexts as an index of articulatory flexibility that can used to quantify articulatory distinctiveness, and will determine how well this kinematic measure of articulatory distinctiveness predicts intelligibility in children with dysarthria, relative to an acoustic measure of vowel distinctiveness (i.e., acoustic vowel space area). We hypothesize that the amount of variation in tongue coupling, reflecting articulatory distinctiveness of both consonants and vowels, will be a stronger predictor of intelligibility than acoustic vowel space area. The proposed research has important implications for improving theoretical understanding of the biomechanical basis of reduced speech intelligibility in children with dysarthria, and has the potential to lead to improved assessment and treatment techniques that leverage information about articulatory constraints to maximize the efficacy of speech intervention.